Make a chain. 1st Row - Make 1 single crochet in every stitch of the chain. Break off the yarn at end of each row.
2nd Row - Work 1 single crochet in every stitch, always taking the stitch from the back.
3rd Row - Work 1 single crochet, then wrap the yarn twice over the hook for treble crochet, sticking the hook in the top stitch of the 1st row of single crochet; then 3 single crochet, picking up the back stitch only; then the treble, and repeat to the end of the row.
4th Row - Work 2 single crochet, then the treble. This brings the treble back of the one in the preceding row. Then 3 single crochet (the 1 above the treble must be taken through the stitch, the other 2 take up the back stitch). Always have 3 stitches between the trebles; in each row the treble will be 1 stitch back of the treble in the preceding row.
Source: Woolco Knitting & Crocheting Manual